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The Current T2K Beam Window
Design and Upgrade
Potential
Oxford-Princeton Targetry Workshop
Princeton, Nov 2008Matt Rooney
Exploded assembly view
Side plates-Provide a firm support for the beam window and guidance during installation
Top plate- Used for inserting and removing window- Protects pillow seals and mating flanges- Provides a connection point for services
Inflatable seals-Seal helium vessel and beam line
Ti-6Al-4V beam window
Ti-6Al-4V Beam window
- Some difficulties with post-machining and post-weld distortion – a common problem with Ti-6Al-4V.- E-beam welding conducted by Culham UKAEA Special Techniques Group.
Helium cooling
He in He out
Titanium - 0.3mm
Titanium -0.3mm
Helium3mm Gap
Upstream
He gap
Downstream
Helium velocity ≈ 5 m/sHeat transfer coefficient ≈ 150 W/m2K
Inflatable seals
Picture courtesy of Y. Miyake andS. Makimura (KEK)
Picture courtesy of PSI
PSI
KEK Muon Group
Pillow seals
outer diaphragm
inner diaphragm
bellows
Pictures courtesy of Y. Miyake (KEK)
pressure line
vacuum line
~ 200 mm
Window – side viewSection view
KEK Muon Group pillow seal
Seal and mating flange
Seal foils (surface roughness, Ra = 0.004 µm, Rt = 0.030 µm)
Polished flange (surface roughness, Ra = 0.020 µm)
Seals manufactured by UHV Design in UK.Developed from similar design at KEK (via Oak Ridge via PSI).
Beam properties
0
1E+14
2E+14
3E+14
4E+14
5E+14
6E+14
7E+14
8E+14
9E+14
0 0.005 0.01 0.015 0.02
Radius (m)
Hea
t (J
/m2)
- 0.75 MW beam power- 3.3 x 1014 protons per pulse- Gaussian profile with 4 mm rad rms beam spot- 5 µs pulse = 8 x 58ns bunches- 1 pulse every 2 seconds at 30 GeV
Energy deposited in window with distance from beam centre
ANSYS Static Stress Results
UTS Ti-6Al-4V ≈ 1GPa
NOTE: 100W/m2K heat transfer coefficient applied to internal wall
Stresses at Centre of 150mm Diameter Hemisphere
0
20
40
60
80
100
120
140
0 0.2 0.4 0.6 0.8 1
Thickness at Beam Centre (mm)
Vo
n M
ise
s S
tre
ss
(M
Pa
)
0
100
200
300
400
Te
mp
era
ture
(o
C)
Thermal Stress
Pressure Stress
Combined Stress
Temperature
0
10
20
30
40
50
60
70
80
90
0 5 10 15 20 25 30
Time (s)
VM
str
es
s (
MP
a)
Inner edge
Outer edge
Centre
-200
-150
-100
-50
0
50
100
150
200
0 1 2 3 4 5
Time from beginning of pulse (μs)
Str
es
s (
MP
a)
Von Mises
Hoop
Longitudinal
Transient thermal stress over multiple pulses
Stress waves developing over pulse
Ti-6Al-4V – the good news
0
100
200
300
400
500
600
700
800
900
1000
0.E+00 1.E+06 2.E+06 3.E+06 4.E+06 5.E+06 6.E+06 7.E+06 8.E+06 9.E+06
Number of cycles
Ma
xim
um
str
es
s (
MP
a)
Fatigue strength
Stress @ 0.75 MW
Safety factor of 4-5
Yield strength
T2K beam window upgrade potential
Increased number of protons per pulse would push the limits of Ti-6Al-4V.
0.75 MW pulse ~ 100 MPa shock stress3.0 MW pulse ~ 500 MPa shock stress
Room temp yield strength Ti-6Al-4V = 900 MPa.But higher power could also be achieved through a higher beam frequency.
0
100
200
300
400
500
600
0 50000 100000 150000 200000 250000 300000 350000
Heat deposit (J/g)
Pe
ak
str
es
s (
MP
a)
VM centre
Long centre
VM edge
Stress Analysis Overview
- Long term survival of window looks likely for 0.75 MW beam.- Beam upgrades with increased PPP would test the limits of the material.- Potential for power upgrades more promising if number of pulses is increased. - Radiation damage then becomes the dominant factor in determining live in service.